This invention relates to apparatus for cutting metal workpieces by melting the workpieces with a melting tool such as a plasma-arc torch. The invention more particularly relates to apparatus in which a melting tool such as a plasma-arc torch acts in conjunction with a punch press for forming holes in the workpiece. The combination of a punch press and a plasma-arc torch is disclosed in Swanson United States application Ser. No. 688,966, filed May 24, 1976 and assigned to the assignee of the present invention.
As disclosed in the Swanson application, the punch press includes a reciprocating punch which coacts with a die to form comparatively small and substantially regularly shaped holes in the workpiece. The latter is supported on a table which is adapted to be moved in a fore-and-aft direction relative to the punch. Carried on the table and movable relative thereto in a transverse direction is a clamp which is adapted to grip one edge of the workpiece. By shifting the table in a fore-and-aft direction and by shifting the clamp in the transverse direction, various areas of the workpiece may be positioned beneath the punch to enable holes to be punched at selected locations in the workpiece.
The movable table and the movable clamp also are used to position the workpiece beneath the plasma-arc torch, the latter being used to cut sections from the workpiece and to form large and irregularly shaped holes in the workpiece. The torch operates by ionizing a column of gas with an electric arc to produce temperatures up to 30,000.degree. F. A high velocity, high temperature plasma stream and electric arc strike the workpiece with the heat serving to instantly melt the metal while the high velocity stream blows away the molten metal.
In the apparatus disclosed in the Swanson application, a duct extends upwardly through the work table and is disposed beneath the workpiece in alinement with the torch. Molten metal falls downwardly into the duct for collection and periodic removal while fumes are sucked into the duct and away from the work area by a vacuum system. Prior to the fumes being discharged from the vacuum system, foreign particles are filtered from the fumes in order to provide a relatively clean discharge to atmosphere.